This invention relates to a tunnel monitoring system for monitoring vehicle traffic in a tunnel.
Tunnel monitoring systems of various designs for monitoring vehicles in a tunnel are generally known. A tunnel monitoring system is known, for example, in which fire reporting devices are installed in the longitudinal direction of the tunnel. This system is designed to detect and locate a possible fire in the tunnel, in particular a burning vehicle. This system can comprise controls actuating automatic warning devices, traffic guiding devices or locking devices in case of a detected fire. Such a monitoring system is suited exclusively for the recognition of dangerous situations due to fire.
Another prior tunnel monitoring system consists of several monitoring cameras installed at intervals along the tunnel. Assigned tunnel segments can be monitored visually, and events detected by a camera are shown on a screen at a tunnel monitoring command station and evaluated by a monitoring person. It is also a known method to install such monitoring cameras so as to be capable of swiveling, whereby a swiveling motion can be remote-controlled at the tunnel monitoring command station. Such a tunnel monitoring system with monitoring cameras is cost intensive in acquisition and maintenance. The function of camera lenses in particular is restricted when they become soiled by developing smoke in case of critical fires. Furthermore, the system automatic recognition and evaluation of imminent danger situations is not possible, or is only possible to a limited extent since a relatively long tunnel segment with possibly a number of vehicles is covered and autonomous image evaluation is difficult. Thus, the evaluation of the image information supplied by such a tunnel monitoring system becomes essentially the responsibility of a monitoring person at the tunnel monitoring command station with respect to recognition of dangerous situations, evaluation of the density of traffic, of travel speeds and distances kept, etc. Protection essentially depends on the individual alertness of a monitoring person, and rapid recognition of a dangerous situation together with required rapid responses is not ensured.
The two previously described known tunnel monitoring systems, the fire reporting devices and the monitoring cameras, can be used in the manner of locating sensors of vehicles to locate vehicles in normal operating and/or in dangerous situations, however with the necessary acceptance of the above-mentioned disadvantages and weaknesses of the system.
Another traffic monitoring system is disclosed in U.S. Pat. No. 5,528,234 in which data sensed by ultrasonic sensors is subjected to a statistic evaluation in a central station regarding vehicle speed and vehicle density. Based on this evaluation, the current traffic conditions are assessed. Traffic conditions can then be transmitted in form of messages from the central station. The operation of a specific vehicle is not considered in this case, so that this traffic monitoring system does not evaluate the current and precise data concerning specific traffic situations, but only the improvement of traffic safety.
In another tunnel monitoring system (JP-A 282 581) sound sensors are distributed and installed along the longitudinal course of a tunnel, whereby the immobility of a vehicle in the tunnel is detected and located. Control of problem-free passage of a vehicle through the tunnel is not possible with this system.
Accordingly, an object of the present invention is to provide a system for improving traffic safety in a tunnel for vehicle traffic.